Definition of Breslow thickness

Breslow thickness: A method for determining the prognosis with melanoma. The thickness of a melanoma is related to the 5-year survival rate after surgical removal of the tumor.

Named for the physician Alexander Breslow who in 1975 observed that as the thickness of the tumor increases, the chance of survival goes down. For example, a thickness of the melanoma of less than 1.0 millimeters is associated with a 5-year survival of 97% of patients whereas a tumor thickness of more than 8.0 millimeters is associated with 5-year survival of 32%.

The Breslow thickness has come into wider use than an older system, the Clark level of invasion, a method devised by the pathologist Wallace Clark for measuring the depth of penetration of a melanoma into the skin according to anatomic layer (the epidermis, dermis, and the subcutis) of deepest tumor penetration.